1. Field of the Invention
The present invention relates generally to systems for production of liquefied gases, and, more particularly, to control of systems for production of liquefied oxygen in a non-industrial environment.
2. Description of the Related Art
For patients having a need for home based oxygen therapy, compressed gas tank deliveries can be inconvenient and expensive. Oxygen tanks provide a limited supply and require a great deal of storage space within the home, particularly where a patient's usage is high. As a result, there is a need for systems for generating oxygen in the home, such that an essentially unlimited supply of oxygen can be provided.
Home oxygen concentrators, typically employing a pressure swing adsorption system to separate oxygen from air, are capable of providing continuous oxygen delivery in the range of about 1-6 liters per minute. In general, for trips outside the home, patients using oxygen concentrators carry oxygen tanks that are delivered by an outside vendor, supplemental to the concentrator.
As an alternative to separate tanks, certain systems exist that make use of a further condenser system for liquefying the gaseous oxygen and storing it for future use. For traveling, the liquid oxygen is transferred to a portable unit to be carried by the patient. The portable units can carry several hours supply of oxygen in liquid form, allowing the patient to be independent both of the home concentrator and of expendable compressed gas tanks One such system is disclosed in U.S. Pat. No. 5,893,275, the contents of which are herein incorporated by reference.